PAX6 Suppresses the Invasiveness of Glioblastoma Cells and the Expression of the Matrix Metalloproteinase-2 Gene

Abstract

Glioblastoma multiforme (GBM) is the most invasive brain tumor. We have previously reported that the transcription factor PAX6 suppresses the tumorigenecity of GBM cells. By an in vitro Matrigel invasion assay on two GBM cell lines stably transfected with wild-type and/or two mutant forms of PAX6, this study displays the first evidence that PAX6 inhibits the invasiveness of GBM cells and that the DNA-binding domain of PAX6 is required for this function. Using real-time quantitative reverse transcription-PCR (RT-PCR), gelatin zymography, and immunohistochemistry assays, the expression of the gene encoding matrix metalloproteinase-2 (MMP2) in GBM cell lines grown in vitro or in intracranial xenografts in nude mice was shown to be repressed by either stable or adenoviralmediated overexpression of PAX6. Luciferase promoter assays revealed PAX6-mediated suppression of MMP2 promoter activity. Electrophoretic mobility shift assays showed direct binding of PAX6 to the MMP2 promoter. A significant reverse correlation (P < 0.05) occurred between PAX6 and MMP2 expression quantified by real-time quantitative RT-PCR in 41 GBMs, 43 anaplastic astrocytomas, and 7 adjacent normal tissues. Interestingly, the degree and significance of the reverse correlation increased after excluding astrocytomas, whereas it became insignificant after excluding GBMs. In GBM cells stably transfected with a dominant negative mutant PAX6 showing increased MMP2 expression and invasiveness, knockdown of MMP2 revealed that MMP2 is one of the PAX6 target genes mediating its suppression of invasion. Overall data delineated a mechanism for the suppressive function of PAX6 in GBM: suppression of cell invasion by repressing the expression of proinvasive genes such as MMP2. (Cancer Res 2006; 66(20): 9809-17)

MicroRNA-375 targets PAX6 and inhibits the viability, migration and invasion of human breast cancer MCF-7 cells

“…Thus, the suppressive role of miR-375 in the regulation of MCF-7 cell migration and invasion may occur via mediation of other targets. It has been demonstrated that PAX6 mediates cell invasion in different types of cancer, including lung cancer (16), glioma (18), glioblastoma (35,36) and colorectal cancer (19). Therefore, the role of PAX6 in cancer cell metastasis may potentially be tumor-specific.…”

PAX6, a novel target of miR-335, inhibits cell proliferation and invasion in glioma cells

“…Accumulating evidence has demonstrated that PAX6 is crucial in the development of the central nervous system (3). Previously, several studies have suggested that PAX6 acts as a tumor suppressor in malignant glioma (4,5). As one of the most common types of primary brain cancer, the prognosis of malignant glioma is very poor, mainly due to its resistance to radiotherapy, chemotherapy or adjuvant therapies (6)(7)(8).…”

Gliomas induce and exploit microglial MT1-MMP expression for tumor expansion

“…contributed equally to this work. 2 To whom correspondence should be addressed. E-mail: kettenmann@mdc-berlin.de.…”

“…Degradation of ECM by membrane-bound and secreted metalloproteases facilitates glioma invasion. In particular, the membrane-bound metalloproteases are pivotal for tumor invasion as they very efficiently digest extracellular matrix proteins and also activate secreted metalloproteases (1) like matrix metalloproteinase-2 (MMP-2, also known as gelatinase A), which is one of the major proteases involved in glioma invasion in mouse models (2) and probably also in humans (3). Hence, membrane-inserted metalloproteases like membrane type 1 matrix metalloproteinase (MT1-MMP) can enable gliomas to invade the brain parenchyma as single cells (4).…”